Arlene Foster has told the RHI public inquiry she was directly alerted to a bid to control costs of the Great Britain scheme, but insisted it was not a “burning issue” in Northern Ireland.

Inquiry chairman Sir Patrick Coghlin said the UK government’s then energy minister Greg Barker wrote to Mrs Foster in the early stages of the RHI to inform her of the steps taken to limit spending on the model he was overseeing across the Irish Sea.

The DUP leader replied: “I accept that he wrote to the department and to me in particular and I have already indicated that if that came in I would have seen that correspondence coming in.

“It would then have gone off to the (energy) division for advice back to me as to what I needed to say and I’m sorry I can’t recall what advice was given back to me on that particular letter or letters from minister Barker.”

The inquiry chairman said there must have been a subsequent conversation about controlling costs within the department.

“Whether it was a burning issue or not if you are getting advice from your equivalent minister in GB to say this is what we are doing within six months of the scheme going live and we are also about to consult on digression (lowering the tariff in the face of demand), one would have thought that that might have been something you would have raised with officials or perhaps your special adviser – (to ask) ‘should we be doing something like this?’.

“So whatever way you look at it you as a minister and a department were alerted to the fact of what was happening in GB.”

Mrs Foster responded: “I think that’s correct.”

The DUP leader said she had also been under a wrong impression that the Northern Ireland scheme included an “emergency brake” that would enable it to be suspended if costs spiralled.

“It turns out this is the wrong understanding but I had an understanding that Ofgem (scheme administrators) could suspend the scheme,” she said.

Mrs Foster said she was not made aware about concerns flagged by Ofgem.

It had highlighted the potential ways the scheme could be abused and stressed the need to only subsidise boilers that could be proved to be generating “useful heat” – thus negating the possibility of applicants burning fuel unnecessarily, simply to draw down more RHI money.

Under questioning from counsel to the inquiry David Scoffield QC, Mrs Foster rejected any suggestion she was “passive” and allowed officials to get on with running schemes.

“I don’t think anybody would have described me as a passive minister,” she said.

“I certainly didn’t see my role as interfering in which project management style you were using to monitor this particular scheme.”